The invention relates to a method for transferring data via a fieldbus of process automation technology, as such method is defined in the preamble of claim 1.
In process automation technology, field devices are frequently used, in order to control the flow of an industrial process.
To this end, process variables are registered with the help of sensors, and controlled variables are controlled with the help of actuators.
Field devices for determining flow rate, fill level, pressure difference, temperature, etc. are generally known. They serve for registering the corresponding process variables flow rate, fill level, pressure, temperature, etc., and are most often arranged in the immediate vicinity of the process components of concern.
Examples of actuators are controllable valves, which control the flow rate of a liquid or gas in a section of pipeline.
The field devices are frequently connected via a fieldbus with a control unit, which controls the total process flow. In the control units, the measured values of the individual sensors are evaluated and the appropriate actuators are actuated.
Often, fieldbusses are also connected with superordinated communication networks, which serve for data communication with control systems and with company and/or office equipment. In this way, an integrated communication is possible within a company, from the field level into the various company levels. Besides a bounded communication in the local networks LAN, with appropriate connection, also a worldwide communication via the Internet WAN is possible.
In the control systems, process flow is monitored and visualized. Error reports are recorded there. From the control system, direct access to the individual field devices is also possible. This enables querying and modification of parameter values and configuration data. Additionally, diagnosis functions can also be called-up from the control system.
Recently, in process automation technology, systems have also become know, in the case of which the fieldbus is dispensed with, and the field devices are connected directly with a superordinated communication network. The most wide spread network is Ethernet with TCP/IP. Via this, a compatibility within various company levels and, beyond this, also outside of the company, is possible with the Internet.
Via the company network, emails and process data can, in this way, be transmitted simultaneously.
The superordinated company networks based on Ethernet work according to the client/server principle. Fieldbusses, in contrast, work according to the publisher/subscriber principle. The protocols are correspondingly designed.
The strengths of Ethernet with TCP/IP lie in the monitoring/parametering of plants, or plant parts, as the case may be. For control with distributed intelligence, fieldbusses are, in contrast, better suited.
At present, in the case of fieldbusses, no method for data transmission is known, which is capable of meeting both requirements.